Dawn-dusk asymmetry'' in solar coronal arcade formations

Solar flares/arcades and magnetospheric substorms are believed to have a common physical process: energy release via magnetic reconnection. In substorms, it is known that the reconnection point tends to occur more in the dusk side of the magnetotail than in the dawn side. This asymmetry is called the dawn-dusk asymmetry. However, no one has examined so far the existence of such asymmetry in the solar corona. We investigated the directions of arcade formation and -v(in) x B electric field for 32 events, and found that more arcades successively formed in the direction of the electric field than in the opposite direction. This may be a solar analogue of dawn-dusk asymmetry. We also found that velocity of successive formation of arcades increases with the aspect ratio of the arcade.